Non-metallic gear systems find many useful applications. The advantage of non-metallic gear systems over metal ones include their self-lubricating nature. Avoidance of the need for lubricating oil baths have many benefits. For instance, grain milling is traditionally processed on grinding apparatus referred to as "roll stands." The process involves repeated passage of grain between two counter-rotating, grinding rolls which crush the grain until the desired particle size is achieved. This process is suitable for flour and rice milling, and can also be extended to feed, sugar cane and coffee grinding. Although reference is made to the food industry, it is obvious that such grinders, run on self-lubricating gearing without using oil baths, also find useful application in any industry requiring grinding such as for example, pharmaceuticals.
Ordinarily, each pair of rolls is driven by an individual electric motor operatively connected to the roll stand. Alternatively, the roll pairs can be slaved off from a line shaft where a single larger motor provides power for several roll stands. Various devices can be used to transmit the rotating power to the rolls, such as chains and sprockets, V-belts and sheaves, timing belts and pulleys, or gearing, dependant upon the manufacturer of the roll stand.
Gear driven rolls are typically driven with metal-to-metal, helical gearing, but such systems require running in oil baths which is not preferred, especially in the food industry where contamination is a constant hazard to avoid. The primary source of contamination is from the need for constant changing of the oil and other maintenance work associated with the oil baths.
Additionally, costly man-hours are needed for the oil change and maintenance and the spent oil is itself a toxic waste needing expensive disposal. All of these problems can be avoided with self-lubricating gearing.
Sprocket driven systems are also known and also require the use of an oil bath. Non-gear, dry running systems requiring no oil baths, known in the art currently, involve added complexity and costly refinements to stand designs in order to achieve acceptable counter-rotating rolls. Thus, there is a need in the art for a dry running, gear driven system which offers the simplest stand configuration.
One advantageous aspect of the present invention is the provision of a simple, yet novel, dry, gear driven system. To this end is provided disclosure for a non-metallic gear in combination with a keyless retaining device for enhanced connection to shafts. The gear is additionally cut in non-standard tooth form which results in major changes to the lengths of action for approach and recess and reduces or eliminates high wear approach action associated with standard tooth forms.
Non-metal gears are known. For instance, U.S. Pat. No. 3,081,648 issued to Duer describes a gear mechanism made from thermosetting plastic material such as nylon for lubricant-free operation which alleges minimal wear between gear teeth. U.S. Pat. No. 3,199,364 issued to Dew describes a gear in which the toothed rim portion is said to consist of nylon which is claimed to have high impact strength and alleged self-lubricating qualities. However, these earlier attempts at producing practical non-metal gears were not successful as such gears tended to wear rapidly.
Described and claimed hereinbelow is a novel combination of select non-metal material gears which require no lubrication when used with a metal gear and the application of non-standard tooth geometry to achieve the desired sustained resistance to wear. Until the current disclosure, the industry's application for non-metallic gearing has been one of copying the same parameters as metal gearing.
Metal gearing designers generally use helical gears in oil baths to achieve improved strength and reduce noise. However, the benefits derived from helical gearing is offset by having to overcome axial thrust loads with more costly attachment designs. The present invention, in a preferred embodiment, uses non-metal, spur gearing where the design is simplified and offers other features such as reduced loads on bearings. However, the non-standard tooth configuration aspect of the present invention is applicable in both spur and helical gearing and is claimed as such hereinbelow.
Many methods for attaching components to drive shafts are known. For instance, U.S. Pat. No. 4,345,851 issued to Soussloff describes keyless mounting devices for anchoring machine elements to rotary shafts. U.S. Pat. No. 4,615,640 issued to Hosokawa also describes mounting devices for connecting "wheel-like" bodies to shafts. Typical problems encountered in such currently known devices include the need for close tolerances on the shaft and bores to achieve a fit that will not cause fretting corrosion or galling. However, these modifications cause the components to "freeze" to the shafts, making removal such as for maintenance very difficult.
Thus, there is a need in the art to provide improved non-metal gearing with superior shaft connections without the accompanying shortcomings and drawbacks of the prior art.